This invention relates to a dynamoelectric machine, or electrical generator, and, more particularly, to a coolant gas flow separator baffle which is installed in the generator structure to control and divert coolant gas into certain gas coolant passages in the generator structure.
Dynamoelectric machines comprise an annular core structure or stator, of an axially extending, stacked array, of sheet metal lamina. The annular laminate core structure includes axially extending radial slots for receiving electrical conductors in the interior peripheral surface which defines the cylindrical bore of the stator. A cylindrical rotor is concentrically positioned in the bore of the stator for rotation therein. The rotor also includes radially inwardly and axially extending slots in its peripheral surface. The defined slots in the rotor are adapted to receive electrical conductor coils or conductor bars to establish a predetermined magnetic field in the rotor when energized, so that rotation of the rotor carries the magnetic field past conductor bars which are disposed in the axially extending slots in the stator, and electrical current is thereby induced in the stator conductor bars, or armature. In the operation of a dynamoelectric machine a considerable amount of heat is generated in the stator core structure and special cooling is required.
The rotor is disposed within the annular core in spaced relationship to the stator so that there is an annular space between the inner circumference of the annular core and the periphery of the rotor. This space is typically referred to as the gap region or air gap, regardless of the type of cooling gas used. Cooling gas, such as hydrogen, is introduced through gas cooling passages into the interior of the rotor and emerges therefrom through apertures in the circumference of the rotor. In the stator core, there are complementary radially extending passages directly opposite the apertures of the rotor. Cooling gas from the rotor flows across the air gap and into the corresponding stator passages to cool the stator core. It is also a common practice to have a fan element connected to and rotating with the rotor to provide a coolant gas stream to flow axially into the air gap at an axial end thereof. However, forced axial gas flow through and along the air gap causes a disruption in the radial coolant gas flow between the rotor and the stator. Accordingly, various gas control means are employed in the air gap to control and direct cooling gas from the fan for optimum cooling purposes. One such gas control means in the form of a baffle member is described and claimed in U.S. Pat. No. 3,413,499--Barton, assigned to the same assignee as the present invention.
One problem associated with the use of baffles in the air gap is caused by the minimum clearances generally utilized between a stationary baffle and the rotor. Ordinarily, these baffles are mounted on the stator core prior to assembly of the rotor therein. In large dynamoelectric machines the rotor is of great weight, say on the order of several tens of tons. Its assembly and precise alignment are quite difficult to achieve with respect to minimum present baffle clearances, and damage to the baffle may occur with subsequent operation of the machine. An attempt to minimize the minimum clearance problem of a seal between the rotor and the stator by the use of a flexible material baffle is disclosed in U.S. Pat. No. 4,264,834--Armor, assigned to the same assignee as the present invention. If the baffle member is made of a frangible material, breakage may occur with pieces and parts falling into the air gap. These problems are best minimized by the use of a baffle member which can be mounted in its design position after assembly of the rotor in the stator core. Another problem associated with baffles in the air gap is vibration. There may be rather extensive vibration in a dynamoelectric during operation. Baffles are usually fixedly connected to the stator core and contact with the rotor is avoided by appropriate spacing therefrom. However, vibration in the stator core may progressively weaken the baffle mounting with a subsequent change in the minimum clearance, or, in some cases may lead to breakage of the baffle material in the air gap. In addition, vibration of the generator during operation, for example, and the cantilevered effect obtained by the baffle of the Barton patent, may subject the radial outer portion of flange 21 thereof to undesirable contact with the stator, such that damage to flange 21 may occur, with a resultant loss in gas sealing efficiency. The material of the Barton baffle is not described. However, FIG. 2 thereof shows the baffle as one piece, sectioned for metallic construction.
Accordingly, it is an object of this invention to provide gas flow baffle means in the air gap of a dynamoelectric machine which may be mounted in the air gap after assembly of the rotor in the stator and is, therefore, defined as a removable baffle.
Another object of this invention is to provide gas flow baffle means in an air gap of a dynamoelectric machine where the baffle member is both fixed to the stator for mounting purposes and also contacts the stator at a predetermined location from an axial end of the air gap by means of a flexible flange for fuller control of cooling gas flow in the dynamoelectric machine.